1. Field Of The Invention
The present invention relates to a blood oxygenator and temperature control apparatus. More specifically, the present invention relates to a blood oxygenator forming a disposable component of a heat exchanger having as its other component a durable heat source member. The two components are unitable in heat exchange relation. Alternatively, the blood oxygenator may also include any one or all of a blood pump, venous reservoir or auxiliary heat exchange component.
2. Description of the Related Art
Extracorporeal blood oxygenation systems are well known for pumping and/or oxygenating a patient's blood during cardiovascular surgery or other procedures. The blood oxygenation system replaces or supplements the normal physiological lung function of replacing the carbon dioxide in venous blood with oxygen for the arterial blood system. The blood oxygenator typically includes a venous reservoir, a heat exchanger, a blood pump and a blood oxygenator. The venous reservoir provides a supply of venous blood to be oxygenated, the heat exchanger maintains the blood temperature at the "normal thermic" temperature or at a sub-normal temperature, depending on the procedure, the blood pump provides blood transport from the venous reservoir (or other source such as venous blood tubing) to an oxygenator input, through the oxygenator and to the output for return to the patient, and the oxygenator provides a suitable membrane for exchange of carbon dioxide for oxygen.
Some prior blood oxygenation systems, such as that described by Bringham et al., U.S. Pat. No. 4,698,207, integrated several of the major components of the blood oxygenation system, namely the venous reservoir, the heat exchanger and the oxygenator. Such an integrated system, while permitting placement close to the patient may still require a substantial volume of priming blood or fluid. Of course, the prior oxygenator systems with separate blood pump and connecting conduits required even more priming blood or fluid volume. Furthermore, the increase in blood volume within the extracorporeal circuit undesirably increases the volume of blood and/or blood products which must be administered by transfusion during the procedure. A large priming volume increases the amount of non-physiologic matter with which the blood contacts as the blood travels through the blood oxygenation system, thereby increasing the potential for mechanical, chemical and/or immunoreactive damage to the blood. Non-blood priming solutions also cause hematocrit dilution. A large priming volume increases blood-wetted surface area which must be treated with antithrombolytic compounds, such as heparin, and also can increase hemolysis (blood damage). Also, a large priming volume ordinarily means a significant volume of blood is not reinfused to a patient at the conclusion of a surgical procedure.
In the oxygenator, a bundle of hollow oxygenation membrane fibers provide the transport mechanism for the oxygen/carbon dioxide exchange. The fibers are formed from gas permeable membrane material allowing the oxygen to permeate through to the venous blood being pumped past the fiber exteriors while carbon dioxide permeates in the opposite direction. Necessarily, patient blood comes into contact with the oxygenator surfaces, requiring disposal after use.
With prior blood oxygenator systems having separate components, for example, separate venous reservoir, blood pump, oxygenator, and heat exchanger, a large number of component parts, and interconnecting conduits must be assembled. This multiplicity of components presents a high cost, assembly time burden, chance for error, plural leakage paths and contamination vectors, and added clutter and complexity in the operating room. Skilled attention must also be paid upon disassembly of the system to avoid blood contact, and to properly identify and separate durable from disposable components.
In view of the above, a need is recognized for a blood oxygenating system utilizing, to the extent desired or practicable, a combination of durable and disposable components integrating a disposable blood oxygenator/heat exchanger with minimum priming volume and blood-wetted surface area, decreased blood damage and opportunity for foreign surface contact and contamination entry, all with a durable heat source component. Reuse of the heat source component of the heat exchanger would provide a safer oxygenator system. Because the oxygenator/heat exchanger component and the heat-source heat exchanger component would be separate parts each with their own fluid boundary walls, double or redundant boundary wall separation between blood and heat transfer media (water, perhaps) would be provided by the oxygenator/heat exchanger.
Further to the above, a need is recognized to further advantageously combine the above-described oxygenator/heat exchanger with a blood pump also having durable and disposable components in unit with the durable and disposable components, respectively, of the oxygenator/heat exchanger. Those skilled in the pertinent art will quickly recognize the increased ease and convenience of use and decreased costs of manufacture and use associated with such a combination. Importantly, the risks of error in set up, contamination paths, leak paths, and priming volume are all potentially reduced by such a combination. Thus, and further to the above, the need is recognized for such a combination also integrating a venous reservoir integrated with the disposable components of the system so that a detached hard or soft reservoir need not be employed. Of course, each such successive step of integration potentially offers incremental improvement of the advantages outlined above.